Morpholine derivative

ABSTRACT

and to a pharmaceutically suitable acid addition salt thereof with a good affinity to the trace amine associated receptors (TAARs), especially for TAAR1, for the treatment of certain CNS diseases.

The present invention relates to a compound of formula

and to a pharmaceutically suitable acid addition salt thereof.

The compound disclosed herein and covered by Formula I above may exhibit tautomerism. It is intended that the invention encompasses any tautomeric form of this compound, or mixtures of such forms, and is not limited to any one tautomeric form depicted in the formula above.

It has now been found that the compound of formula I (5-ethyl-4-methyl-N-[4-[(2S) morpholin-2-yl]phenyl]-1H-pyrazole-3-carboxamide) has a good affinity to the trace amine associated receptors (TAARs), especially for TAAR1, and less side effects compared with compounds of the prior art.

Similar ligands of mouse TAAR1 and rat TAAR1 have been disclosed in WO2011/076678 and WO2012/16826.

The compound of formula I and its pharmaceutically usable addition salts possess valuable pharmacological properties. Specifically, it has been found that the compound of the present invention is a partial agonist of the human trace amine associated receptor 1 (hTAAR1).

The compound of the present invention has significant advantages over compounds of the prior art, which advantages are

-   -   potent agonistic activity at the human TAAR1 receptor,     -   selectivity against the dopamine transporter (DAT),     -   selectivity against the hERG ion channel,     -   a low amphiphilic vector and thereby posing a low risk of         causing drug-induced phospholipidosis (DIPL) (vide infra).

The compound of formula I may therefore be used as a safe drug for the treatment of depression, anxiety disorders, bipolar disorder, attention deficit hyperactivity disorder (ADHD), stress-related disorders, psychotic disorders such as schizophrenia, neurological diseases such as Parkinson's disease, neurodegenerative disorders such as Alzheimer's disease, epilepsy, migraine, hypertension, addiction, substance abuse and metabolic disorders such as eating disorders, diabetes, diabetic complications, obesity, dyslipidemia, disorders of energy consumption and assimilation, disorders and malfunction of body temperature homeostasis, disorders of sleep and circadian rhythm, and cardiovascular disorders.

The classical biogenic amines (serotonin, norepinephrine, epinephrine, dopamine, histamine) play important roles as neurotransmitters in the central and peripheral nervous system^([1]). Their synthesis and storage, as well as their degradation and reuptake after release, are tightly regulated. An imbalance in the levels of biogenic amines is known to be responsible for the altered brain function under many pathological conditions^([2-5]). A second class of endogenous amine compounds, the so-called trace amines (TAs), significantly overlaps with the classical biogenic amines regarding structure, metabolism and subcellular localization. The TAs include p-tyramine, β-phenylethylamine, tryptamine and octopamine, and they are present in the mammalian nervous system at generally lower levels than classical biogenic amines^([6]).

Dysregulation of TAs has been linked to various psychiatric diseases like schizophrenia and depression^([7]) and to other conditions like attention deficit hyperactivity disorder, migraine headache, Parkinson's disease, substance abuse and eating disorders^([8,9]).

For a long time, TA-specific receptors had only been hypothesized based on anatomically discrete high-affinity TA binding sites in the CNS of humans and other mammals^([10,11]). Accordingly, the pharmacological effects of TAs were believed to be mediated through the well-known machinery of classical biogenic amines, by either triggering their release, inhibiting their reuptake or by “cross-reacting” with their receptor systems^([9,12,13]). This view changed significantly with the identification of several members of a novel family of GPCRs, the trace amine-associated receptors (TAARs)^([7,14]). There are 9 TAAR genes in human (including 3 pseudogenes) and 16 genes in mouse (including 1 pseudogene). The TAAR genes do not contain introns (with one exception, TAAR2 contains 1 intron) and are located next to each other on the same chromosomal segment. The phylogenetic relationship of the receptor genes, in agreement with an in-depth GPCR pharmacophore similarity comparison, and pharmacological data suggest that these receptors form three distinct subfamilies^([7,14]). TAAR1 is in the first subclass of four genes (TAAR1-4) highly conserved between human and rodents. TAs activate TAAR1 via G_(α)s. Dysregulation of TAs was shown to contribute to the aetiology of various diseases like depression, anxiety disorders, bipolar disorder, attention deficit hyperactivity disorder (ADHD), stress-related disorders, psychotic disorders such as schizophrenia, neurological diseases such as Parkinson's disease, neurodegenerative disorders such as Alzheimer's disease, epilepsy, migraine, hypertension, addiction, substance abuse and metabolic disorders such as eating disorders, diabetes, diabetic complications, obesity, dyslipidemia, disorders of energy consumption and assimilation, disorders and malfunction of body temperature homeostasis, disorders of sleep and circadian rhythm, and cardiovascular disorders.

Therefore, there is a broad interest to increase the knowledge about trace amine-associated receptors.

LITERATURE REFERENCES

-   [1] Deutch, A. Y. and Roth, R. H.; “Neurotransmitters.” In     Fundamental Neuroscience (2^(nd) Edn) (Zigmond, M. J., Bloom, F. E.,     Landis, S. C., Roberts, J. L, and Squire, L. R., Eds.), pp. 193-234,     Academic Press (1999); -   [2] Wong, M. L. and Licinio, J.; “Research and treatment approaches     to depression.” Nat. Rev. Neurosci. 2001, 2, 343-351; -   [3] Carlsson, A. et al.; “Interactions between monoamines,     glutamate, and GABA in schizophrenia: new evidence.” Annu. Rev.     Pharmacol. Toxicol. 2001, 41, 237-260; -   [4] Tuite, P. and Riss, J.; “Recent developments in the     pharmacological treatment of Parkinson's disease.” Expert Opin.     Investig. Drugs 2003, 12, 1335-1352; -   [5] Castellanos, F. X. and Tannock, R.; “Neuroscience of     attention-deficit/hyperactivity disorder: the search for     endophenotypes.” Nat. Rev. Neurosci. 2002, 3, 617-628; -   [6] Usdin, Earl; Sandler, Merton; Editors; Psychopharmacology     Series, Vol. 1: Trace Amines and the Brain. [Proceedings of a Study     Group at the 14th Annual Meeting of the American College of     Neuropsychoparmacology, San Juan, Puerto Rico] (1976); -   [7] Lindemann, L. and Hoener, M.; “A renaissance in trace amines     inspired by a novel GPCR family.” Trends in Pharmacol. Sci. 2005,     26, 274-281; -   [8] Branchek, T. A. and Blackburn, T. P.; “Trace amine receptors as     targets for novel therapeutics: legend, myth and fact.” Curr. Opin.     Pharmacol. 2003, 3, 90-97; -   [9] Premont, R. T. et al.; “Following the trace of elusive amines.”     Proc. Natl. Acad. Sci. USA 2001, 98, 9474-9475; -   [10] Mousseau, D. D. and Butterworth, R. F.; “A high-affinity [³H]     tryptamine binding site in human brain.” Prog. Brain Res. 1995, 106,     285-291; -   [11] McCormack, J. K. et al.; “Autoradiographic localization of     tryptamine binding sites in the rat and dog central nervous     system.” J. Neurosci. 1986, 6, 94-101; -   [12] Dyck, L. E.; “Release of some endogenous trace amines from rat     striatal slices in the presence and absence of a monoamine oxidase     inhibitor.” Life Sci. 1989, 44, 1149-1156; -   [13] Parker, E. M. and Cubeddu, L. X.; “Comparative effects of     amphetamine, phenylethylamine and related drugs on dopamine efflux,     dopamine uptake and mazindol binding.” J. Pharmacol. Exp. Ther.     1988, 245, 199-210; -   [14] Lindemann, L. et al.; “Trace amine associated receptors form     structurally and functionally distinct subfamilies of novel G     protein-coupled receptors.” Genomics 2005, 85, 372-385.

Objects of the present invention are the new compound of formula I and its pharmaceutically acceptable salts, their use for the treatment of diseases related to the biological function of the trace amine associated receptors, their manufacture and medicaments based on the compound in accordance with the invention in the control or prevention of illnesses such as depression, anxiety disorders, bipolar disorder, attention deficit hyperactivity disorder, stress-related disorders, psychotic disorders such as schizophrenia, neurological diseases such as Parkinson's disease, neurodegenerative disorders such as Alzheimer's disease, epilepsy, migraine, substance abuse, addiction and metabolic disorders such as eating disorders, diabetes, diabetic complications, obesity, dyslipidemia, disorders of energy consumption and assimilation, disorders and malfunction of body temperature homeostasis, disorders of sleep and circadian rhythm, and cardiovascular disorders.

The present compound of formula I and its pharmaceutically acceptable salts can be prepared by methods known in the art, for example, by processes described below, which process comprises

a) cleaving off the N-protecting group (PG) from compounds of formula

to a compound of formula

wherein PG is a N-protecting group selected from —C(O)O-tert-butyl (BOC), and,

if desired, converting the compound obtained into pharmaceutically acceptable acid addition salts.

The starting materials 1,1′ and 2 are commercially available or may be prepared by methods well known in the art. Racemic tert-butyl 2-(4-aminophenyl)morpholine-4-carboxylate (CAS RN: 1002726-96-6) is commercially available. tert-Butyl (2R)-2-(4-aminophenyl)morpholine-4-carboxylate (CAS RN: 1260220-42-5) is commercially available. tert-Butyl (2S)-2-(4-aminophenyl)morpholine-4-carboxylate (CAS RN: 1260220-43-6) is commercially available, or can be prepared as described in the literature, for instance as described in Trussardi, R. & Iding, H, PCT Int. Appl. WO 2015/086495 A1.

Step A: Amide bond formation can be accomplished by a coupling reaction between amine 2 and carboxylic acid compound 1 in the presence of a coupling reagent such as DCC, EDC, TBTU or HATU in the presence of an organic base such as triethylamine, N,N-diisopropylethylamine or N-methylmorpholine in halogenated solvents such as dichloromethane or 1,2-dichloroethane or ethereal solvents such as diethyl ether, dioxane, THF, DME or TBME.

Preferred conditions are TBTU with N-methylmorpholine in THF at 50-60° C. for 12-48 hours. Alternatively, amide bond formation can be accomplished by a coupling reaction between amine 2 and acyl chloride compound 1′ in halogenated solvents such as dichloromethane or 1,2-dichloroethane or ethereal solvents such as diethyl ether, dioxane, THF, DME or TBME, in the presence of an organic base such as triethylamine or N,N-diisopropylethylamine.

Preferred conditions are triethylamine in THF at room temperature for 18 hours.

If desired, the acyl chloride compound 1′ may be prepared in situ from the corresponding carboxylic acid 1 by treatment with oxalyl chloride in halogenated solvents such as dichloromethane or 1,2-dichloroethane or ethereal solvents such as diethyl ether, dioxane, THF, DME or TBME in the presence of a catalyst such as DMF.

Preferred conditions are dichloroethane at room temperature for 1 hour.

Alternatively, the acyl chloride compound 1′ may be prepared in situ from the corresponding carboxylic acid 1 by treatment with 1-chloro-N,N,2-trimethylpropenylamine [CAS 26189-59-3] in dichoromethane, followed by removal of the solvent in vacuo, according to the method of Ghosez and co-workers (J. Chem. Soc., Chem. Commun. 1979, 1180; Org. Synth. 1980, 59, 26-34).

Step B: Removal of the BOC N-protecting group can be effected with mineral acids such as HCl, H₂SO₄ or H₃PO₄ or organic acids such as CF₃COOH, CHCl₂COOH, HOAc or p-toluenesulfonic acid in solvents such as CH₂Cl₂, CHCl₃, THF, MeOH, EtOH or H₂O at 0 to 80° C.

Preferred conditions are CF₃COOH in aqueous acetonitrile at 80° C. for 3 hours or 4 N HCl in dioxane at room temperature for 16 hours.

Where racemic starting material 2 has been used, the resulting racemic mixture of morpholine compounds I′ may be separated into its constituent enantiomers by using chiral HPLC. Alternatively, compound I may be obtained in enantiomerically pure form by starting from enantiomerically pure compound 2.

Isolation and Purification of the Compounds

Isolation and purification of the compounds and intermediates described herein can be effected, if desired, by any suitable separation or purification procedure such as, for example, filtration, extraction, crystallization, column chromatography, thin-layer chromatography, thick-layer chromatography, preparative low or high-pressure liquid chromatography or a combination of these procedures. Specific illustrations of suitable separation and isolation procedures can be had by reference to the preparations and examples herein below. However, other equivalent separation or isolation procedures could, of course, also be used. Racemic mixtures of chiral compounds of formula I can be separated using chiral HPLC. Racemic mixtures of chiral synthetic intermediates may also be separated using chiral HPLC.

Salts of Compound of Formula I

The compound of formula I is basic and may be converted to a corresponding acid addition salt. The conversion is accomplished by treatment with at least a stoichiometric amount of an appropriate acid, such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid and the like, and organic acids such as acetic acid, propionic acid, glycolic acid, pyruvic acid, oxalic acid, malic acid, malonic acid, succinic acid, maleic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, salicylic acid and the like. Typically, the free base is dissolved in an inert organic solvent such as diethyl ether, ethyl acetate, chloroform, ethanol or methanol and the like, and the acid added in a similar solvent. The temperature is maintained between 0° C. and 50° C. The resulting salt precipitates spontaneously or may be brought out of solution with a less polar solvent.

EXAMPLE 1 5-Ethyl-4-methyl-N-[4-[(2S)-morpholin-2-yl]phenyl]-1H-pyrazole-3-carboxamide

a) tert-Butyl (2S)-2-[4-[(5-ethyl-4-methyl-1H-pyrazole-3-carbonyl)amino]phenyl]morpholine-4-carboxylate

To a stirred solution of tert-butyl (2S)-2-(4-aminophenyl)morpholine-4-carboxylate (CAS RN: 1260220-43-6, 350 mg, 1.26 mmol, 1.00 equiv.) and 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid (CAS RN: 957129-38-3, 245 mg, 1.51 mmol, 1.20 equiv.) in THF (8 ml) were added TBTU (807 mg, 2.51 mmol, 2.00 equiv.) and N-methylmorpholine (509 mg, 553 μl, 5.03 mmol, 4.00 equiv.). The reaction mixture was stirred at 50° C. for 15 h. TLC at t=15 h showed the reaction was complete. The reaction mixture was concentrated in vacuo. The crude material was purified by flash chromatography (silica gel, eluant: 0% to 100% EtOAc in heptane) to afford tert-butyl (2S)-2-[4-[(5-ethyl-4-methyl-1H-pyrazole-3-carbonyl)amino]phenyl]morpholine-4-carboxylate as an off-white solid (501 mg, 96%). MS (ISP): 413.7 ([M−H]⁻).

b) 5-Ethyl-4-methyl-N-[4-[(2S)-morpholin-2-yl]phenyl]-1H-pyrazole-3-carboxamide

To a stirred solution of trifluoroacetic acid (1.37 g, 918 μl, 12.0 mmol, 10 equiv.) in water (8 ml) was added a suspension of tert-butyl (2S)-2-[4-[(5-ethyl-4-methyl-1H-pyrazole-3-carbonyl)amino]phenyl]morpholine-4-carboxylate (497 mg, 1.2 mmol, 1.00 equiv.) in acetonitrile (4 ml). The reaction mixture was stirred at 80° C. for 3 h. MS at t=3 h showed the reaction was complete. The reaction mixture was poured into 1 M aq. NaOH and extracted twice with EtOAc. The organic layers were dried over Na₂SO₄ and concentrated in vacuo. The crude material was purified by flash column chromatography (SiliaSep™ amine cartridge, eluant: 0% to 100% EtOAc in heptane, then 0% to 10% MeOH in EtOAc) to afford 5-ethyl-4-methyl-N-[4-[(2S)-morpholin-2-yl]phenyl]-1H-pyrazole-3-carboxamide (327 mg, 87%) as an off-white solid. MS (ISP): 315.7 ([M+H]⁺).

EXAMPLE 2 (COMPARATIVE EXAMPLE) 5-Ethyl-4-methyl-N-[4-[(2R)-morpholin-2-yl]phenyl]-1H-pyrazole-3-carboxamide

The title compound was obtained in analogy to example 1 using (2R)-2-(4-aminophenyl)morpholine-4-carboxylate (CAS RN: 1260220-42-5) in place of (2S)-2-(4-aminophenyl)morpholine-4-carboxylate in step (a). White solid. MS (ISP): 315.6 ([M+H]⁺).

EXAMPLE 3 (COMPARATIVE EXAMPLE) N-[4-[(2S)-Morpholin-2-yl]phenyl]-6-(2,2,2-trifluoroethoxy)pyridine-3-carboxamide

The title compound was obtained in analogy to example 1 using 6-(2,2,2-trifluoroethoxy)nicotinic acid (CAS RN: 159783-29-6) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 382.1 ([M+H]⁺).

EXAMPLE 4 (COMPARATIVE EXAMPLE) 6-Chloro-N-[4-[(2S)-morpholin-2-yl]phenyl]pyridine-3-carboxamide

The title compound was obtained in analogy to example 1 using 6-chloro-nicotinic acid (CAS RN: 5326-23-8) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 320.1 ([{³⁷Cl}M+H]⁺), 318.2 ([{³⁵Cl}M+H]⁺).

EXAMPLE 5 (COMPARATIVE EXAMPLE) 2-Chloro-N-[4-[(2S)-morpholin-2-yl]phenyl]pyridine-4-carboxamide

The title compound was obtained in analogy to example 1 using 2-chloro-isonicotinic acid (CAS RN: 6313-54-8) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 320.1 ([{³⁷Cl}M+H]⁺), 318.1 ([{³⁵Cl}M+H]⁺).

EXAMPLE 6 (COMPARATIVE EXAMPLE) N-[4-[(2S)-Morpholin-2-yl]phenyl]-2-phenyl-1,3-thiazole-5-carboxamide

The title compound was obtained in analogy to example 1 using 2-phenylthiazole-5-carboxylic acid (CAS RN: 10058-38-5) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 366.1 ([M+H]⁺).

EXAMPLE 7 (COMPARATIVE EXAMPLE) 2,6-Dichloro-N-[4[(2S)-morpholin-2-yl]phenyl] pyridine-4-carboxamide

The title compound was obtained in analogy to example 1 using 2,6-dichloro-isonicotinic acid (CAS RN: 5398-44-7) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 356.1 ([{³⁷Cl}M+H]⁺), 354.1 ([{³⁷Cl³⁵Cl}M+H]⁺), 352.1 ([{³⁵Cl}M+H]⁺).

EXAMPLE 8 (COMPARATIVE EXAMPLE) 4-Methyl-N-[4-[(2S)-morpholin-2-yl]phenyl]-5-phenyl-1H-pyrazole-3-carboxamide

The title compound was obtained in analogy to example 1 using 4-methyl-5-phenyl-1H-pyrazole-3-carboxylic acid (CAS RN: 879770-33-9) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 363.2 ([M+H]⁺).

EXAMPLE 9 (COMPARATIVE EXAMPLE) 5,6-Dichloro-N-[4-[(2S)-morpholin-2-yl]phenyl]pyridine-3-carboxamide

The title compound was obtained in analogy to example 1 using 5,6-dichloro-nicotinic acid (CAS RN: 41667-95-2) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 356.1 ([{³⁷Cl³⁵Cl}M+H]⁺), 354.1 ([{³⁷Cl}M+H]⁺), 352.1 ([{³⁵Cl}M+H]⁺).

EXAMPLE 10 (COMPARATIVE EXAMPLE) 6-Cyano-N-[4-[(2S)-morpholin-2-yl]phenyl] pyridine-3-carboxamide

The title compound was obtained in analogy to example 1 using 6-cyano-nicotinic acid (CAS RN: 70165-31-0) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 309.1 ([M+H]⁺).

EXAMPLE 11 (COMPARATIVE EXAMPLE) N-[4-[(2S)-Morpholin-2-yl]phenyl]-6-(trifluoromethyl)pyridine-3-carboxamide

The title compound was obtained in analogy to example 1 using 6-(trifluoromethyl)nicotinic acid (CAS RN: 158063-66-2) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 352.2 ([M+H]⁺).

EXAMPLE 12 (COMPARATIVE EXAMPLE) 5-Chloro-N-[4-[(2S)-morpholin-2-yl]phenyl]pyridine-2-carboxamide

The title compound was obtained in analogy to example 1 using 5-chloro-picolinic acid (CAS RN: 86873-60-1) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 320.1 ([{³⁷Cl}M+H]⁺), 318.2 ([{³⁵Cl}M+H]⁺).

EXAMPLE 13 (COMPARATIVE EXAMPLE) 5-Chloro-N-[4-[(2S)-morpholin-2-yl]phenyl]pyridine-3-carboxamide

The title compound was obtained in analogy to example 1 using 5-chloro-nicotinic acid (CAS RN: 22620-27-5) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 320.1 ([{³⁷Cl}M+H]⁺), 318.1 ([{³⁵Cl}M+H]⁺).

EXAMPLE 14 (COMPARATIVE EXAMPLE) 2-Chloro-6-methyl-N-[4-[(2S)-morpholin-2-yl]phenyl]pyridine-4-carboxamide

The title compound was obtained in analogy to example 1 using 2-chloro-6-methylpyridine-4-carboxylic acid (CAS RN: 25462-85-5) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 334.1 ([{³⁷Cl}M+H]⁺), 332.1 ([{³⁵Cl}M+H]⁺).

EXAMPLE 15 (COMPARATIVE EXAMPLE) N-[4-[(2S)-Morpholin-2-yl]phenyl]-2-phenyl-1,3-oxazole-4-carboxamide

The title compound was obtained in analogy to example 1 using 2-phenyloxazole-4-carboxylic acid (CAS RN: 23012-16-0) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 350.2 ([M+H]⁺).

EXAMPLE 16 (COMPARATIVE EXAMPLE) N-[4-[(2S)-Morpholin-2-yl]phenyl]-2-phenyl-1,3-thiazole-4-carboxamide

The title compound was obtained in analogy to example 1 using 2-phenylthiazole-4-carboxylic acid (CAS RN: 7113-10-2) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 366.1 ([M+H]⁺).

EXAMPLE 17 (COMPARATIVE EXAMPLE) 2-Methyl-N-[4-[(2S)-morpholin-2-yl]phenyl] pyridine-4-carboxamide

The title compound was obtained in analogy to example 1 using 2-methyl-isonicotinic acid (CAS RN: 4021-11-8) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 298.2 ([M+H]⁺).

EXAMPLE 18 (COMPARATIVE EXAMPLE) 2,6-Dimethyl-N-[4-[(2S)-morpholin-2-yl]phenyl] pyridine-4-carboxamide

The title compound was obtained in analogy to example 1 using 2,6-dimethyl-isonicotinic acid (CAS RN: 54221-93-1) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 312.2 ([M+H]⁺).

EXAMPLE 19 (COMPARATIVE EXAMPLE) N-[4-[(2S)-Morpholin-2-yl]phenyl]-2-methyl-1,3-thiazole-4-carboxamide

The title compound was obtained in analogy to example 1 using 2-methylthiazole-4-carboxylic acid (CAS RN: 35272-15-2) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 304.1 ([M+H]⁺).

EXAMPLE 20 (COMPARATIVE EXAMPLE) N-[4-[(2S)-Morpholin-2-yl]phenyl]-1-phenylpyrazole-3-carboxamide

The title compound was obtained in analogy to example 1 using 1-phenyl-1H-pyrazole-3-carboxylic acid (CAS RN: 4747-46-0) in place of 5-ethyl-4-methyl-1H-pyrazole-3-carboxylic acid in step (a). White solid. MS (ISP): 349.2 ([M+H]⁺).

As mentioned above, the compound of the present invention has significant advantages over compounds of the prior art, which advantages are potent agonistic activity at the human TAAR1 receptor, selectivity against the dopamine transporter (DAT), selectivity against the hERG ion channel, and a low amphiphilic vector and thereby posing a low risk of causing drug-induced phospholipidosis (DIPL) (vide infra).

The following comparative data and comments may be provided to show the superiority advantages of the compound of formula I in comparison with known compounds of the prior art.

1. Pharmacological Effects and Therapeutic Potential of Partial Agonists of the Human Trace Amine-Associated Receptor 1 (hTAAR1)

There is evidence of significant species differences in ligand-receptor interactions between rodent and human TAAR1^([1]). Therefore, when selecting compounds for use as human therapeutics for the treatment of TAAR1-related diseases it is important to prioritize candidate compounds based on the potency of their functional activity at the human form of the TAAR1 receptor (hTAAR1). hTAAR1 is a G protein-coupled transmembrane receptor (GPCR), whereby ligands may function as antagonists, agonists, partial agonists or inverse agonists of the receptor. The compound of formula I and comparative examples have been tested in vitro for functional activity at hTAAR1, whereby the compound of formula I was found to be a partial agonist of hTAAR1. The experimentally determined hTAAR1 EC₅₀ values for the compound of formula I and a selection of comparative examples are shown in Table 1 (vide infra). The compound of example 1 has thereby been found, in particular, to be a potent partial agonist of hTAAR1 in vitro.

Ex vivo electrophysiology experiments in the ventral tegmental area and dorsal raphe nuclei showed that TAAR1 partial agonists enhanced DA and 5-HT neuron firing rates in wild-type mice^([2,3]), whereas full agonists like p-tyramine decreased firing rates^([3,4]). However, both full and partial agonists have been shown to be protective against the rewarding and reinforcing effects of the psychostimulant cocaine^([5]). Whereas full agonists like amphetamine induce negative feedback to blunt their own effect on DA and 5-HT systems^([6,7]), partial agonists might increase their effect on neuronal signal transmission by increasing firing rates via TAAR1. Because of these findings, and the reports that TAAR1 partial agonists have a richer in vivo pharmacology in rodents than full agonists^([3,8]), a strong body of preclinical evidence is emerging which suggests that TAAR1 partial agonists show highly promising potential for use as human therapeutics for the treatment of CNS diseases including, but not limited to, schizophrenia, bipolar disorder, depression, Parkinson's disease, as well as for the treatment of alcohol and drug addiction.

For instance, TAAR1 partial agonists are proposed to be superior to existing atypical antipsychotic drugs by displaying antipsychotic efficacy with the benefit of improved cognition and mood as well as with a reduced side effect profile (e.g. no induction of the metabolic syndrome which is seen with current antipsychotics)^([3,8]). Other literature suggests possible indications include bipolar disorder,^([8]) drug addiction^([5,9]), and diabetes^([10]).

LITERATURE REFERENCES

-   [1] Simmler, L. D.; Buchy, D.; Chaboz, S.; Hoener, M. C.;     Liechti, M. E.; “In vitro characterization of psychoactive     substances at rat, mouse and human trace amine-associated receptor     1”. J. Pharmacol. Exp. Ther. 2016, Fast Forward article DOI:     10.1124/jpet.115.229765; -   [2] Bradaia, A. et al.; “The selective antagonist EPPTB reveals     TAAR1-mediated regulatory mechanisms in dopaminergic neurons of the     mesolimbic system”. Proc. Nat. Acad. Sci. USA 2009, 106,     20081-20086; -   [3] Revel, F. G. et al.; “Trace amine-associated receptor 1 partial     agonism reveals novel paradigm for neuropsychiatric therapeutics”.     Biol. Psychiatry 2012, 72, 934-942; -   [4] Revel, F. G. et al.; “TAAR1 activation modulates monoaminergic     neurotransmission, preventing hyperdopaminergic and     hypoglutamatergic activity”. Proc. Nat. Acad. Sci. USA 2011, 108,     8485-8490; -   [5] Pei, Y.; Mortas, P.; Hoener, M. C.; Canales, J. J.; “Selective     activation of the trace amine-associated receptor 1 decreases     cocaine's reinforcing efficacy and prevents cocaine-induced changes     in brain reward thresholds”. Prog. Neuro-Psychopharmacol. & Biol.     Psychiatry 2015, 63, 70-75; -   [6] Lindemann, L. et al.; “Trace amine-associated receptor 1     modulates dopaminergic activity”. J. Pharmacol. Exp. Ther. 2008,     324, 948-956; -   [7] Di Cara, B. et al.; “Genetic deletion of trace amine 1 receptors     reveals their role in auto-inhibiting the actions of ecstasy     (MDMA)”. J. Neuroscience 2011, 31, 16928-16940; -   [8] Revel, F. G. et al.; “A new perspective for schizophrenia: TAAR1     agonists reveal antipsychotic- and antidepressant-like activity,     improve cognition and control body weight”. Mol. Psychiatry 2013,     18, 543-556; -   [9] Pei, Y.; Lee, J.; Leo, D.; Gainetdinov, R. R.; Hoener, M. C.;     Canales, J. J.; “Activation of the trace amine-associated receptor 1     prevents relapse to cocaine seeking”. Neuropsychopharmacology 2014,     39, 2299-2308; -   [10] Raab, S. et al.; “Incretin-like effects of small molecule trace     amine-associated receptor 1 agonists”. Mol. Metabolism 2016, 5,     47-56.

2. Dopamine Transporter (DAT) and Associated Liability for Drug Abuse and/or Addiction Potential

The pharmacology of the dopamine transporter (DAT) has been implicated inter alia in the psychostimulatory effects and in the abuse liability and addiction mechanism of certain psychostimulant drugs such as cocaine and MDPV.^([1-3]) Therefore, for a new therapeutic intended for human use, it is desirable to avoid inhibition of, or interaction with, the dopamine transporter DAT in order to minimize the risk of abuse liability or potential for addiction.

For instance, evidence suggests that cocaine's reinforcing effects depend on its ability to rapidly block the dopamine transporter (DAT). In animal studies, dopamine reuptake inhibitors other than cocaine are also self-administered, with a relative potency that generally correlates positively with their potency in inhibiting the DAT, but not the serotonin or norepinephrine transporters (SERT, NET)[⁴⁻⁸]. Animals trained to self-administer cocaine will also self-administer direct dopamine agonists^([9-11]). In addition, destruction of dopamine nerve terminals can lead to extinction of cocaine self-administration behavior^([12,13]), and these effects have been observed even when responding maintained by other reinforcers was preserved^([14,15]). In humans, cocaine-induced “high” correlates with DAT occupancy in the brain^([16]).

To further test the hypothesis that DAT is essential to cocaine's reinforcing effects, a functional but “cocaine-insensitive” DAT was generated and expressed in mice^([17,18]). This mutant DAT demonstrated an 89-fold lower affinity for cocaine relative to wild-type DAT, and cocaine failed to increase extracellular dopamine in the nucleus accumbens, or to induce increases in locomotor activity, stereotypies, or conditioned place preferences, in knock-in (DATki) mice expressing this mutant DAT^([18-20]). In addition, cocaine failed to serve as a positive reinforcer in these DATki mice, whereas food, d-amphetamine, and a direct dopamine agonist reliably maintained operant behavior in these mice, at levels comparable with wild-type mice^([21]). Reintroduction of the cocaine-sensitive wild type DAT to brain areas including inter alia the ventral tegmental area (VTA) led to restoration of cocaine reward behavior in the DATki mice^([22]). In conclusion, cocaine's ability to block DAT is sufficient to abolish its reinforcing effects in mice providing strong evidence that DAT blockade is critical for cocaine's reinforcing effects.

Therefore, taken together, these findings suggest that for a new therapeutic intended for human use, it is highly desirable to avoid inhibition of, or interaction with, the dopamine transporter DAT in order to minimize the risk of abuse liability or potential for addiction.

The measured in vitro DAT K_(i) for a series of TAAR1 compounds are shown in Table 1 (vide infra). It has surprisingly been found that Example 1 is a significantly weaker ligand at DAT than other compounds, while simultaneously being a potent partial agonist of hTAAR1, and therefore the hTAAR1/DAT selectivity ratio for Example 1 is significantly higher than for other compounds.

LITERATURE REFERENCES

-   [1] Meil, W. M. and Boja, J. W.; “The dopamine transporter and     addiction.” Chapter 1, pp. 1-21 in Neurochemistry of Abused Drugs     (Karch, S. B., Ed.), CRC Press (2008); -   [2] Simmler, L. D. et al.; “Pharmacological characterization of     designer cathinones in vitro”. Brit. J. Pharmacol. 2013, 168,     458-470; -   [3] Baumann, M. H.; Partilla, J. S.; Lehner, K. R.; “Psychoactive     ‘bath salts’: not so soothing”. Eur. J. Pharmacol. 2013, 698, 1-5; -   [4] Ritz., M. C.; Lamb, R. J.; Goldberg, S. R.; Kuhar, M. J.;     “Cocaine receptors on dopamine transporters are related to     self-administration of cocaine”. Science 1987, 237, 1219-1223; -   [5] Bergmann., J.; Madras, B. K.; Johnson, S. E.; Spealman, R. D.;     “Effects of cocaine and relared drugs in nonhuman primates. III.     Self-administration by squirrel monkeys”. J. Pharmacol. Exp. Ther.     1989, 251, 150-155; -   [6] Howell., L. L. & Byrd, L. D.; “Serotonergic modulation of the     behavioural effects of cocaine in the squirrel monkey”. J.     Pharmacol. Exp. Ther. 1995, 275, 1551-1559; -   [7] Roberts, D. C. S. et al.; “Self-administration of cocaine     analogs by rats”. Psychopharmacology 1999, 144, 389-397; -   [8] Wee, S. et al.; “Relationship between serotonergic activity and     reinforcing effects of a series of amphetamine analogs”. J.     Pharmacol. Exp. Ther. 2005, 313, 848-854; -   [9] Woolverton, W. L.; Goldberg, L. I.; Ginos, J. Z.; “Intravenous     self-administration of dopamine receptor agonists by Rhesus     monkeys”. J. Pharmacol. Exp. Ther. 1984, 230, 678-683; -   [10] Wise, R. A.; Murray, A.; Bozarth, M. A.; “Bromocriptine     self-administration and bromocriptine-reinstatement of     cocaine-trained and heroin-trained lever pressing in rats”.     Psychopharmacology 1990, 100, 355-360; -   [11] Caine, S. B. & Koob, G. F.; “Modulation of cocaine     self-administration in the rat through D-3 dopamine receptors”.     Science 1993, 260, 1814-1816; -   [12] Roberts, D. C. S.; Corcoran, M. E.; Fibiger, H. C.; “On the     role of ascending catecholaminergic systems in intravenous     self-administration of cocaine”. Pharmacol. Biochem. Behaviour 1977,     6, 615-620; -   [13] Roberts, D. C. S.; Koob, G. F.; Klonoff, P.; Fibiger, H. C.;     “Extinction and recovery of cocaine self-administration following     6-hydroxydopamine lesions of the nucleus accumbens”. Pharmacol.     Biochem. Behaviour 1980, 12, 781-787; -   [14] Pettit, H. O.; Ettenberg, A.; Bloom, F. E.; Koob, G. F.;     “Destruction of dopamine in the nucleus accumbens selectively     attenuates cocaine but not heroin self-administration in rats”.     Psychopharmacology 1984, 84, 167-173; -   [15] Caine, S. B. & Koob, G. F.; “Effects of mesolimbic dopamine     depletion on responding maintained by cocaine and food”. J. Exp.     Anal. Behavior 1994, 61, 213-221; -   [16] Volkow, N. D. et al.; “Relationship between subjective effects     of cocaine and dopamine transporter occupancy”. Nature 1997, 386,     827-830; -   [17] Chen, R.; Han, D. D.; Gu, H. H.; “A triple mutation in the     second transmembrane domain of mouse dopamine transporter markedly     decreases sensitivity to cocaine and methylphenidate”. J. Neurochem.     2005, 94, 352-359; -   [18] Chen, R. et al.; “Abolished cocaine reward in mice with a     cocaine-insensitive dopamine transporter”. Proc. Nat. Acad. Sci. USA     2006, 103, 9333-9338; -   [19] Tilley, M. R. & Gu, H. H.; “Dopamine transporter inhibition is     required for cocaine-induced stereotypy”. Neuroreport 2008, 19,     1137-1140; -   [20] Tilley, M. R.; O'Neill, B.; Han, D. D.; Gu, H. H.; “Cocaine     does not produce reward in absence of dopamine transporter     inhibition”. Neuroreport 2009, 20, 9-12; -   [21] Thomsen, M.; Han, D. D.; Gu, H. H.; Caine, S. B.; “Lack of     cocaine self-administration in mice expressing a cocaine-insensitive     dopamine transporter”. J. Pharmacol. Exp. Ther. 2009, 331, 204-211; -   [22] Wu, H. et al.; “Restoration of cocaine stimulation and reward     by reintroducing wild type dopamine transporter in adult knock-in     mice with a cocaine-insensitive dopamine transporter”.     Neuropharmacology 2014, 86, 31-37.

3. hERG Blockade and Associated Liability for Cardiac QT Interval Prolongation

Minimization of the likelihood to cause drug-induced cardiac side effects is highly desirable for a therapeutic agent intended for safe use in humans, especially for a drug intended to be used for chronic treatment regimens. In recent years, regulatory authorities have delayed approval or imposed restrictions on the use of, and even denied approval or removed from the market, therapeutic agents prolonging the cardiac QT interval. The QT interval is the time from the beginning of the QRS complex to the end of the T wave of the electrocardiogram (ECG) and is a measure of the duration of ventricular depolarization and repolarization. Drugs prolonging the QT interval have been associated with a polymorphic ventricular tachycardia referred to as Torsades de Pointes (TdP). This arrhythmia can cause serious cardiovascular outcomes and can progress to irreversible ventricular fibrillation and death. The ICH S7B regulatory guideline^([1]) recommends an overall non-clinical strategy for evaluating cardiovascular risk of new molecular entities (NMEs) which includes the in vitro IK_(r) assay [potassium current conducted by the human ether-a-go-go related gene (hERG)]. Inhibition of hERG was identified as the major mechanism for QT prolongation.^([2]) Therefore, the recommended minimal non-clinical QT interval de-risking strategy is to test representative compounds from a given chemical series in the in vitro hERG assay.^([3]) The goal is to select compounds causing no more than 20% hERG inhibition at concentrations at least 30-fold below the efficacious in vitro (or in vivo if available) concentration for therapeutic activity. In the case of TAAR1 agonists, the hTAAR1 EC₅₀ can be considered as the relevant in vitro concentration predictive of therapeutic activity (vide supra). Therefore it is desirable to select TAAR1 agonists where the ratio hERG IC₂₀/hTAAR1 EC₅₀ is at least 30-fold.

The measured in vitro hERG IC₂₀ and IC₅₀ for a series of TAAR1 compounds are shown in Table 1 (vide infra).

Basic compounds in particular are known to be especially prone to causing potent inhibition of the hERG channel.^([4]) All of the TAAR1 compounds bear the same morpholino head group, therefore all compounds are expected to be similarly basic. The basic moiety is required for agonist activity at hTAAR1. It has surprisingly been found that Example 1 is a significantly weaker hERG channel inhibitor than comparative compounds, and therefore the hERG IC₂₀/hTAAR1 EC₅₀ ratio for Example 1 is significantly higher than the recommended 30-fold minimum.

LITERATURE REFERENCES

-   [1] ICH Guideline. “The nonclinical evaluation of the potential for     delayed ventricular repolarization (QT interval prolongation) by     human pharmaceuticals (S7B)” issued as CPMP/ICH/423/02, adopted by     CHMP in May 2005;     http://www.ich.org/products/guidelines/safety/safety-single/article/the-non-clinical-evaluation-of-the-potential-for-delayed-ventricular-repolarization-qt-interval-pro.html -   [2] Redfern, W. S.; Carlsson, L.; Davis, A. S.; Lynch, W. G.;     MacKenzie, I.; Palethorpe, S.; Siegl, P. K.; Strang, I; Sullivan, A.     T.; Wallis, R.; Camm, A. J.; Hammond, T. G.; “Relationships between     preclinical cardiac electrophysiology, clinical QT interval     prolongation and torsade de pointes for a broad range of drugs:     evidence for a provisional safety margin in drug development”.     Cardiovasc. Res. 2003, 58, 32-45; -   [3] Helliwell, R. M.: “Potassium Channels”. Methods in Molecular     Biology (Totowa, N.J., United States) 2008, 491, 279-295; -   [4] Zolotoy, A. B.; Plouvier, B. P.; Beatch, G. B.; Hayes, E. S.;     Wall, R. A.; Walker, M. J. A.; “Physicochemical determinants for     drug-induced blockade of hERG potassium channels: Effect of charge     and charge shielding”. Curr. Med. Chem.—Cardiovascular &     Hematological Agents 2003, 1, 225-241.

4. Amphiphilicity and Associated Liability for Drug-Induced Phospholipidosis (DIPL)

Phospholipidosis (PLD) is a lysosomal storage disorder characterized by the excess accumulation of phospholipids in tissues^([1][2][3]) Many cationic amphiphilic drugs, including anti-depressants, antianginal, antimalarial, and cholesterol-lowering agents, are reported to cause drug-induced phospholipidosis (DIPL) in animals and humans. The mechanisms of DIPL involve trapping or selective uptake of DIPL drugs within the lysosomes and acidic vesicles of affected cells. Drug-trapping is followed by a gradual accumulation of drug-phospholipid complexes within the internal lysosomal membranes. The increase in undigested materials results in the abnormal accumulation of multi-lammellar bodies (myeloid bodies) in tissues. Although phospholipidosis is primarily considered to be a storage disorder, with some compounds the storage disorder is known to be associated with inflammation and necrosis leading to functional impairment of the affected tissues. It is therefore highly desirable that a therapeutic drug should not pose a risk for causing DIPL. This is especially true in the case of medicines intended for chronic use, for instance, drugs intended for the treatment of chronic psychiatric disorders such as schizophrenia, bipolar disorder or depression, or drugs intended for the treatment of chronic metabolic disorders such as diabetes.

DIPL is an adverse effect known to be particularly associated with cationic amphiphilic drugs (CAD).^([4]) To avoid DIPL either the basic pK_(a) (basic pK_(a)<6.3) or the amphiphilicity (ΔΔG_(am)>−6 kJ mol⁻¹) of a compound has to be reduced (i.e. ΔΔG_(am) needs to be increased).^([5]) A compound is classified as DIPL negative if either the basic pK_(a) value is below 6.3 or the amphiphilicity is above ΔΔG_(am)=−6 kJ mol⁻¹. The amphiphilicity for a given compound can be calculated in silico directly from the molecular structural formula,^([6]) and therefore the predicted risk for DIPL for that compound can also be calculated in silico,^([5]) whereby the prediction algorithm uses a DIPL risk classification defined according to the following criteria, which are based on parameters extracted from a computational training set comprising experimentally determined phospholipidosis results for a large set of compounds:

AMPHIPHILIC VECTOR>−5.0 kJ/mol and BPKA1<=5.60 results in NEGATIVE DIPL prediction;

−7.0 kJ/mol<AMPHIPHILIC VECTOR<−5.0 kJ/mol and/or 7.0>BPKA1>5.60 results in BORDERLINE DIPL prediction;

AMPHIPHILIC VECTOR<−7.0 kJ/mol and BPKA1>=7.00 results in POSITIVE DIPL prediction.

The calculated amphiphilicities (ΔΔG_(am) in kJ mol⁻¹) as well as the in silico DIPL risk predictions (negative/borderline/positive) for a series of TAAR1 compounds are shown in Table 1 (vide infra).

All of the TAAR1 compounds bear the same morpholino head group, therefore the basic pK_(a) of all compounds is very similar and clearly above 6.3. The basic moiety is required for agonist activity at hTAAR1. Therefore, the only way to avoid DIPL is to reduce the lipophilicity of the backbone of the molecules. It has surprisingly been found that for Example 1 the lipophilicity is reduced significantly more than expected based on the results for similar compounds, and therefore the amphiphilicity of Example 1 is clearly reduced and, as a consequence, this compound is not predicted to cause DIPL.

LITERATURE REFERENCES

-   [1] Anderson, N.; Borlak, J.; “Drug-induced phospholipidosis”. FEBS     Lett. 2006, 580, 5533-540; -   [2] Reasor, M. J.; Hastings, K. L.; Ulrich, R. G.; “Drug-induced     phospholipidosis: issues and future directions”. Expert Opin. Drug     Safety 2006, 5, 567-83; -   [3] Nonoyama, T.; Fukuda, R.; “Drug induced phospholipidosis     pathological aspects and its prediction”. J. Toxicol. Pathol. 2008,     21, 9-24; -   [4] Lullmann, H.; Lullmann-Rauch, R.; Wassermann, O.; “Lipidosis     induced by amphiphilic cationic drugs.” Biochem. Pharmacol. 1978,     27, 1103-8; -   [5] Fischer, H.; Atzpodien, E. A.; Csato, M; Doessegger, L.; Lenz,     B.; Schmitt, G.; Singer, T.; “In silico assay for assessing     phospholipidosis potential of small drug like molecules: training,     validation and refinement using several datasets.” J. Med. Chem.     2012, 55, 126-139; -   [6] Fischer, H.; Kansy, M.; Bur, D.; “CAFCA: a novel tool for the     calculation of amphiphilic properties of charged drug molecules”.     Chimia 2000, 54, 640-645.

The compounds were investigated in accordance with the tests given hereinafter.

Materials and Methods

Human TAAR1

For the construction of expression plasmids the coding sequences of human TAAR1 were amplified from genomic DNA essentially as described by Lindemann et al. [14]. The Expand High Fidelity PCR System (Roche Diagnostics) was used with 1.5 mM Mg²⁺ and purified PCR products were cloned into pCR2.1-TOPO cloning vector (Invitrogen) following the instructions of the manufacturer. PCR products were subcloned into the pIRESneo2 vector (BD Clontech, Palo Alto, Calif.), and expression vectors were sequence verified before introduction in cell lines.

HEK293 cells (ATCC #CRL-1573) were cultured essentially as described by Lindemann et al. (2005). For the generation of stably transfected cell lines HEK293 cells were transfected with the pIRESneo2 expression plasmids containing the TAAR coding sequences (described above) with Lipofectamine 2000 (Invitrogen) according to the instructions of the manufacturer, and 24 hrs post transfection the culture medium was supplemented with 1 mg/ml G418 (Sigma, Buchs, Switzerland). After a culture period of about 10 d clones were isolated, expanded and tested for responsiveness to trace amines (all compounds purchased from Sigma) with the cAMP Biotrak Enzyme immunoassay (EIA) System (Amersham) following the non-acetylation EIA procedure provided by the manufacturer. Monoclonal cell lines which displayed a stable EC₅₀ for a culture period of 15 passages were used for all subsequent studies.

cAMP measurements were performed as described previously (Revel et al., Proc. Natl. Acad. Sci. USA 2011, 108, 8485-8490). In brief, cells that expressed human TAAR1 were plated on 96-well plates (BIOCOAT 6640; Becton Dickinson, Allschwil, Switzerland) and incubated for 20 h at 37° C. Prior to stimulation of the cells with a broad concentration range of agonists for 30 min at 37° C., the cells were washed with PBS and preincubated with PBS that contained 1 mM 3-isobutyl-1-methylxanthine for 10 min at 37° C. and 5% CO₂. Stimulation with 0.2% DMSO was set as the basal level, and the effect of 30 μM β-PEA was set as the maximal response. Subsequently, the cells were lysed, and cAMP assays were performed according to the manufacturer's instructions (cAMP kit; Upstate/Millipore, Schaffhausen, Switzerland). Finally, the plates were read with a luminometer (1420 Multilabel counter; PerkinElmer, Schwerzenbach, Switzerland), and the amount of cAMP was calculated. The results were obtained from at least three independent experiments. Experiments were run in duplicate or triplicate. EC₅₀ values are presented as mean±standard deviation (in μM). The E_(max) value for the functional activity data at TAAR1 describes the degree of functional activity compared with 100% for the endogenous ligand and full agonist β-PEA.

Human DAT

Binding to dopamine transporter (DAT) in vitro. Human embryonic kidney (HEK) 293 cells (Invitrogen, Zug, Switzerland) stably transfected with human DAT were cultured. The cells were collected and washed three times with phosphate-buffered saline (PBS). The pellets were frozen at −80° C. The pellets were then resuspended in 400 ml of 20 mM HEPES-NaOH, pH 7.4, that contained 10 mM EDTA at 4° C. After homogenization with a Polytron (Kinematica, Lucerne, Switzerland) at 10000 rotations per minute (rpm) for 15 s, the homogenates were centrifuged at 48000×g for 30 min at 4° C. Aliquots of the membrane stocks were frozen at −80° C. All assays were performed at least three times. The test compounds were diluted in 20 ml of binding buffer (252 mM NaCl, 5.4 mM KCl, 20 mM Na₂HPO₄, 3.52 mM KH₂PO₄, pH 7.4) and 10 point dilution curves were made and transferred to 96-well white polystyrene assay plates (Sigma-Aldrich, Buchs, Switzerland). [³H]-WIN35,428 (˜86 Ci/mmol; Perkin-Elmer) was the radioligand for the DAT assay and had a K_(d) of 12 nM. Fifty microliters of [³H]-WIN35,428 (˜40 nM concentration) was added to each well of the hDAT assay plates, targeting a final [³H]-WIN35428 concentration of 10 nM. Twenty microliters of binding buffer alone in the assay plate defined the total binding, whereas binding in the presence of 10 μM indatraline defined nonspecific binding. Frozen DAT membrane stocks were thawed and resuspended to a concentration of approximately 0.04 mg protein/ml binding buffer (1:1 diluted in H₂O) using a polytron tissue homogenizer. The membrane homogenates (40 μg/ml) were then lightly mixed for 5-30 min with polyvinyl toluene (PCT) wheat germ agglutinin-coated scintillation proximity assay (WGASPA; Amersham Biosciences) beads at 7.7 mg beads/ml homogenate. One hundred thirty microliters of the membrane/bead mixture were added to each well of the assay plate that contained radioligand and test compounds (final volume in each well, 200 μl) to start the assay, which was incubated for approximately 2 h at room temperature with agitation. The assay plates were then counted in the PVT SPA counting mode of a Packard Topcount. Fifty microliters of the [³H]-WIN35428 stocks were counted in 5 ml of ReadySafe scintillation cocktail (Beckman Industries) on a Packard 1900CA liquid scintillation counter to determine the total counts added to the respective assays. Non-linear regression was used to fit the data to sigmoid curves and determine IC₅₀ values for binding and uptake. K_(i) values for binding and uptake were calculated using the following Cheng-Prusoff equation: K_(i)=IC₅₀/(1+[S]/K_(m)).

Human ERG (hERG)

The whole-cell patch-clamp technique was used to investigate the effects of the test items on hERG (human-ether-a-go-go related gene) potassium channels in stably transfected CHO cells near physiological temperature (36±1° C.). The effects of compounds on hERG K⁺-current parameters were evaluated at 4 concentrations (0.3-3-30-300 μM) in at least 3 CHO cells stably expressing the hERG channel. For electrophysiological measurements cells were seeded onto 35 mm sterile culture dishes containing 2 ml culture medium without Hygromycin B. Cells were cultivated at a density that enabled single cells (without visible connections to neighbouring cells) to be measured. Cells were incubated at 37° C. in a humidified atmosphere with 5% CO₂ (rel. humidity about 95%). The cells were continuously maintained in and passaged in sterile culture flasks containing nutrient mixture F-12 (DMEM/F-12 with L-Glutamine) supplemented with 10% foetal bovine serum and 10% penicillin/streptomycin solution. Every day at least three cells were treated with a selective IK_(r) blocker (E-4031, reference substance) to assure accuracy of the method. The 35 mm culture dishes upon which cells were seeded at a density allowing single cells to be recorded were placed on the dish holder of the microscope and continuously perfused (at approximately 1 ml/min) with the bath solution (sodium chloride 150 mM, potassium chloride 4 mM, calcium chloride 1.2 mM, magnesium chloride 1 mM, HEPES 10 mM, pH (NaOH) 7.4) at near physiological temperature (36±1° C.). After formation of a Gigaohm seal between the patch electrodes and individual hERG stably transfected CHO cells (pipette resistance range: 2.0 MΩ-7.0 MΩ; seal resistance range: >1 GΩ) the cell membrane across the pipette tip was ruptured to assure electrical access to the cell interior (whole-cell patch-configuration). In case the quality of the seal was poor, the process of seal formation was repeated with a different cell and a new pipette. As soon as a stable seal was established, hERG outward tail currents were measured upon depolarization of the cell membrane to −40 mV for 50 ms followed by 500 ms at +20 mV (activation of channels) from a holding potential of −80 mV and upon subsequent repolarization to −40 mV for 500 ms. This voltage protocol was run at least 10 times at intervals of 10 s. If current density was judged to be too low for measurement, another cell was recorded. Once control recordings have been accomplished, cells were continuously perfused with a bath solution containing the test items. During wash-in of the test item the voltage protocol indicated above was run continuously again at 10 s intervals until the steady-state level of block was reached. The four test item concentrations of the compound were applied sequentially to 3 cells in a cumulative manner. As hERG tail currents were inhibited by the test item, the concentration-response curve was generated and IC₅₀ value calculated. Based on the IC₅₀ value the IC₂₀ was estimated. Each concentration of the test item was analyzed in three experiments (n=3).

Amphiphilic Vector (ΔΔG_(am)) Calculation and in Silico DIPL Prediction

Amphiphilic vector (ΔΔG_(am)) and in silico DIPL prediction were computationally determined from the molecular structural formula for the compound of formula I and comparative compounds according to the published algorithms (Fischer, H.; Kansy, M.; Bur, D.; “CAFCA: a novel tool for the calculation of amphiphilic properties of charged drug molecules”. Chimia 2000, 54, 640-645; Fischer, H.; Atzpodien, E. A.; Csato, M; Doessegger, L.; Lenz, B.; Schmitt, G.; Singer, T.; “In silico assay for assessing phospholipidosis potential of small drug like molecules: training, validation and refinement using several datasets.” J. Med. Chem. 2012, 55, 126-139).

The compound of formula I has partial agonist activity on hTAAR1 (EC₅₀ in μM), binding affinity at hDAT (K_(i) in μM), and channel blocking activity at hERG (IC₂₀ and IC₅₀ in μM) as shown in Table 1. Table 1 also shows the calculated amphiphilic vector (ΔΔG_(am) in kJ mol⁻¹) and in silico phospholipidosis estimation (negative/positive/borderline prediction for in vitro DIPL and in vivo DIPL) for the compound of formula I and comparative compounds, as calculated using the procedure described above.

TABLE 1 Ratio hERG Phospho- in silico in silico Ratio hTAAR1 hTAAR1 hERG hERG IC₂₀/ lipidosis Phospho- Phospho- DAT DAT K_(i)/ Example EC₅₀ efficacy* IC₅₀ IC₂₀ hTAAR1 ΔΔG_(am) lipidosis lipidosis K_(i) hTAAR1 No Structure (μM) (%) (μM) (μM) EC₅₀ (kJ mol⁻¹) (in vitro) (in vivo) (μM) EC₅₀  1

0.0585 42 216.60  36.20 619 −3.47 NEGATIVE NEGATIVE   27.53 471  2

0.2632 38 — — — — — — — —  3

0.0377 45  9.84  1.97  52 −6.3  POSITIVE BORDERLINE   17.43 462  4

0.0619 49  49.67  12.42 201 −5.31 NEGATIVE BORDERLINE    2.50  40  5

0.0656 40  81.71  22.16 338 −5.9  NEGATIVE BORDERLINE    1.52  23  6

0.08  30  1.31  0.38  5 −8.46 POSITIVE POSITIVE    5.93  74  7

0.0849 57  11.39  3.67  43 −7.41 POSITIVE POSITIVE    0.79  9  8

0.1086 33  10.78  3.01  28 −4.89 NEGATIVE NEGATIVE    9.77  90  9

0.1437 32  4.46  1.14  8 −8.83 POSITIVE POSITIVE    0.48  3 10

0.1837 38  31.72  5.78  31 −3.11 NEGATIVE NEGATIVE   11.30  62 11

0.2027 46  17.42  2.59  13 −6.18 POSITIVE BORDERLINE    2.33  12 12

0.2119 40  14.26  3.21  15 −6.59 POSITIVE BORDERLINE    1.78  8 13

0.4045 37  66.04  9.14  23 −6.23 POSITIVE BORDERLINE    1.31  3 14

0.4467 53  73.18  21.63  48 −6.96 POSITIVE BORDERLINE    7.32  16 15

0.6632 35  9.65  2.40  4 −7.4  POSITIVE POSITIVE >26.1  >39 16

0.666  35  8.98  3.35  5 −8.48 POSITIVE POSITIVE   16.22  24 17

0.6727 45 518.2  129.55 193 −4.53 NEGATIVE NEGATIVE   10.32  15 18

0.8271 63 711.5  146.78 177 −5.82 NEGATIVE BORDERLINE >26.1  >32 19

1.025  32  60.47  8.32  8 −4.59 NEGATIVE NEGATIVE   21.9   21 20

2.480  59  10.75  2.49  1 −5.37 NEGATIVE BORDERLINE >26.1  >11 *% agonist activity for hTAAR1 is reported on a scale calibrated such that effect of the endogenenous ligand β-phenylethylamine = 100% agonism

It has surprisingly been found that the compound of formula I (example 1) displays an overall superior combination of properties in terms of potent agonist activity at hTAAR1, high selectivity against hDAT, high selectivity against hERG, low amphiphilic vector and consequently low phospholipidosis risk compared to other TAAR1 compounds of the prior art. Inspection of Table 1 reveals that example 1 has potent partial agonist activity at hTAAR1 (EC₅₀=0.059 μM), is highly selective against hDAT (K_(i)=27.5 μM; selectivity ratio=471-fold versus hTAAR1 EC₅₀), is highly selective against hERG (IC₂₀=36.2 μM; selectivity ratio=619-fold versus hTAAR1 EC₅₀) and has a low amphiphilic vector (ΔΔG_(am)=−3.47 kJ mol⁻¹) well below the threshold of concern for phospholipidosis (in silico DIPL risk prediction=negative).

Inspection of Table 1 reveals that close analogues of example 1 have inferior properties compared to example 1 in one or more regards.

For instance, comparative example 2, which is the R enantiomer of example 1, is less potent at hTAAR1 (EC₅₀=0.2632 μM), which teaches that the S configuration of absolute stereochemistry, as in example 1, is preferred in order to obtain higher potency at hTAAR1.

Comparative example 3 is significantly more potent at hERG (IC₂₀=1.97 μM; selectivity ratio=52-fold versus hTAAR1 EC₅₀) and also has a significantly higher amphiphilic vector (ΔΔG_(am)=−6.3 kJ mol⁻¹) and thus a positive DIPL prediction.

Comparative example 4 is significantly more potent at DAT (K_(i)=2.5 μM; selectivity ratio=40-fold versus hTAAR1 EC₅₀) and also has a higher amphiphilic vector (ΔΔG_(am)=−5.3 kJ mol⁻¹) and thus a borderline DIPL prediction.

Comparative example 5 is significantly more potent at DAT (K_(i)=1.5 μM; selectivity ratio=23-fold versus hTAAR1 EC₅₀) and also has a higher amphiphilic vector (ΔΔG_(am)=−5.9 kJ mol⁻¹) and thus a borderline DIPL prediction.

Comparative example 6 is significantly more potent at hERG (IC₂₀=0.38 μM; selectivity ratio=5-fold versus hTAAR1 EC₅₀), is more potent at DAT (K_(i)=5.9 μM; selectivity ratio=74-fold versus hTAAR1 EC₅₀) and also has a significantly higher amphiphilic vector (ΔΔG_(am)=−8.46 kJ mol⁻¹) and thus a positive DIPL prediction.

Comparative example 7 is significantly more potent at hERG (IC₂₀=3.57 μM; selectivity ratio=43-fold versus hTAAR1 EC₅₀), is significantly more potent at DAT (K_(i)=0.79 μM; selectivity ratio=9-fold versus hTAAR1 EC₅₀) and also has a significantly higher amphiphilic vector (ΔΔG_(am)=−7.41 kJ mol⁻¹) and thus a positive DIPL prediction.

Comparative example 8 is significantly more potent at hERG (IC₂₀=3.01 μM; selectivity ratio=28-fold versus hTAAR1 EC₅₀).

Comparative example 9 is less potent at hTAAR1 (EC₅₀=0.144 μM), is significantly more potent at hERG (IC₂₀=1.14 μM; selectivity ratio=8-fold versus hTAAR1 EC₅₀), is significantly more potent at DAT (K_(i)=0.48 μM; selectivity ratio=3-fold versus hTAAR1 EC₅₀) and also has a significantly higher amphiphilic vector (ΔΔG_(am)=−8.83 kJ mol⁻¹) and thus a positive DIPL prediction.

Comparative example 10 is less potent at hTAAR1 (EC₅₀=0.184 μM) and is more potent at hERG (IC₂₀=5.78 μM; selectivity ratio=31-fold versus hTAAR1 EC₅₀).

Comparative example 11 is less potent at hTAAR1 (EC₅₀=0.203 μM), is significantly more potent at hERG (IC₂₀=2.59 μM; selectivity ratio=13-fold versus hTAAR1 EC₅₀), is significantly more potent at DAT (K_(i)=2.33 μM; selectivity ratio=12-fold versus hTAAR1 EC₅₀) and also has a significantly higher amphiphilic vector (ΔΔG_(am)=−6.18 kJ mol⁻¹) and thus a positive DIPL prediction.

Comparative example 12 is less potent at hTAAR1 (EC₅₀=0.212 μM), is significantly more potent at hERG (IC₂₀=3.21 μM; selectivity ratio=15-fold versus hTAAR1 EC₅₀), is significantly more potent at DAT (K_(i)=1.78 μM; selectivity ratio=8-fold versus hTAAR1 EC₅₀) and also has a significantly higher amphiphilic vector (ΔΔG_(am)=−6.59 kJ mol⁻¹) and thus a positive DIPL prediction.

Comparative example 13 is significantly less potent at hTAAR1 (EC₅₀=0.405 μM), is more potent at hERG (IC₂₀=9.14 μM; selectivity ratio=23-fold versus hTAAR1 EC₅₀), is significantly more potent at DAT (K_(i)=1.31 μM; selectivity ratio=3-fold versus hTAAR1 EC₅₀) and also has a significantly higher amphiphilic vector (ΔΔG_(am)=−6.23 kJ mol⁻¹) and thus a positive DIPL prediction.

Comparative example 14 is significantly less potent at hTAAR1 (EC₅₀=0.447 μM), is significantly more potent at DAT (K_(i)=7.32 μM; selectivity ratio=16-fold versus hTAAR1 EC₅₀) and also has a significantly higher amphiphilic vector (ΔΔG_(am)=−6.96 kJ mol⁻¹) and thus a positive DIPL prediction.

Comparative example 15 is significantly less potent at hTAAR1 (EC₅₀=0.663 μM), is significantly more potent at hERG (IC₂₀=2.40 μM; selectivity ratio=4-fold versus hTAAR1 EC₅₀) and also has a significantly higher amphiphilic vector (ΔΔG_(am)=−7.4 kJ mol⁻¹) and thus a positive DIPL prediction.

Comparative example 16 is significantly less potent at hTAAR1 (EC₅₀=0.666 μM), is significantly more potent at hERG (IC₂₀=3.35 μM; selectivity ratio=5-fold versus hTAAR1 EC₅₀) and also has a significantly higher amphiphilic vector (ΔΔG_(am)=−8.48 kJ mol⁻¹) and thus a positive DIPL prediction.

Comparative example 17 is significantly less potent at hTAAR1 (EC₅₀=0.673 μM) and is more potent at DAT (K_(i)=10.32 μM; selectivity ratio=15-fold versus hTAAR1 EC₅₀).

Comparative example 18 is significantly less potent at hTAAR1 (EC₅₀=0.827 μM) and also has a higher amphiphilic vector (ΔΔG_(am)=−5.82 kJ mol⁻¹) and thus a borderline DIPL prediction.

Comparative example 19 is significantly less potent at hTAAR1 (EC₅₀=1.025 μM) and is more potent at hERG (IC₂₀=8.32 μM; selectivity ratio=8-fold versus hTAAR1 EC₅₀).

Finally, comparative example 20 is significantly less potent at hTAAR1 (EC₅₀=2.48 μM), is significantly more potent at hERG (IC₂₀=2.49 μM; selectivity ratio=1-fold versus hTAAR1 EC₅₀) and also has a higher amphiphilic vector (ΔΔG_(am)=−5.37 kJ mol⁻¹) and thus a borderline DIPL prediction.

Therefore, taking all of the data in Table 1 into consideration, the compound of formula I (example 1) is the overall most preferred compound for the intended use as a safe and effective therapeutic agent for treatment in humans of TAAR1-related disorders, especially for the treatment of chronic CNS disorders, such as depression, anxiety disorders, bipolar disorder, attention deficit hyperactivity disorder (ADHD), stress-related disorders, psychotic disorders such as schizophrenia, neurological diseases such as Parkinson's disease, neurodegenerative disorders such as Alzheimer's disease, epilepsy, migraine, hypertension, substance abuse, addiction and metabolic disorders such as eating disorders, diabetes, diabetic complications, obesity, dyslipidemia, disorders of energy consumption and assimilation, disorders and malfunction of body temperature homeostasis, disorders of sleep and circadian rhythm, and cardiovascular disorders. The most preferred disorders are schizophrenia, bipolar disorder or depression.

The compound of formula I and the pharmaceutically acceptable salts of the compound of formula I can be used as medicaments, e.g. in the form of pharmaceutical preparations. The pharmaceutical preparations can be administered orally, e.g. in the form of tablets, coated tablets, dragées, hard and soft gelatine capsules, solutions, emulsions or suspensions. The administration can, however, also be effected rectally, e.g. in the form of suppositories, or parenterally, e.g. in the form of injection solutions.

The compound of formula I can be processed with pharmaceutically inert, inorganic or organic carriers for the production of pharmaceutical preparations. Lactose, corn starch or derivatives thereof, talc, stearic acids or its salts and the like can be used, for example, as such carriers for tablets, coated tablets, dragées and hard gelatine capsules. Suitable carriers for soft gelatine capsules are, for example, vegetable oils, waxes, fats, semi-solid and liquid polyols and the like. Depending on the nature of the active substance no carriers are however usually required in the case of soft gelatine capsules. Suitable carriers for the production of solutions and syrups are, for example, water, polyols, glycerol, vegetable oil and the like. Suitable carriers for suppositories are, for example, natural or hardened oils, waxes, fats, semi-liquid or liquid polyols and the like.

The pharmaceutical preparations can, moreover, contain preservatives, solubilizers, stabilizers, wetting agents, emulsifiers, sweeteners, colorants, flavorants, salts for varying the osmotic pressure, buffers, masking agents or antioxidants. They can also contain still other therapeutically valuable substances.

Medicaments containing a compound of formula I or a pharmaceutically acceptable salt thereof and a therapeutically inert carrier are also an object of the present invention, as is a process for their production, which comprises bringing the compound of formula I and/or pharmaceutically acceptable acid addition salts and, if desired, one or more other therapeutically valuable substances into a galenical administration form together with one or more therapeutically inert carriers.

The most preferred indications in accordance with the present invention are those which include disorders of the central nervous system, for example the treatment or prevention of depression, schizophrenia and bipolar disorders.

The dosage can vary within wide limits and will, of course, have to be adjusted to the individual requirements in each particular case. In the case of oral administration the dosage for adults can vary from about 0.01 mg to about 1000 mg per day of a compound of general formula I or of the corresponding amount of a pharmaceutically acceptable salt thereof. The daily dosage may be administered as single dose or in divided doses and, in addition, the upper limit can also be exceeded when this is found to be indicated.

Tablet Formulation (Wet Granulation)

Item Ingredients mg/tablet 1. Compound of formula I 5 25 100 500 2. Lactose Anhydrous DTG 125 105 30 150 3. Sta-Rx 1500 6 6 6 30 4. Microcrystalline Cellulose 30 30 30 150 5. Magnesium Stearate 1 1 1 1 Total 167 167 167 831

Manufacturing Procedure

1. Mix items 1, 2, 3 and 4 and granulate with purified water.

2. Dry the granules at 50° C.

3. Pass the granules through suitable milling equipment.

4. Add item 5 and mix for three minutes; compress on a suitable press.

Capsule Formulation

Item Ingredients mg/capsule 1. Compound of formula I 5 25 100 500 2. Hydrous Lactose 159 123 148 — 3. Corn Starch 25 35 40 70 4. Talc 10 15 10 25 5. Magnesium Stearate 1 2 2 5 Total 200 200 300 600

Manufacturing Procedure

1. Mix items 1, 2 and 3 in a suitable mixer for 30 minutes.

2. Add items 4 and 5 and mix for 3 minutes.

3. Fill into a suitable capsule. 

1. A morpholine derivative of formula

and a pharmaceutically suitable acid addition salt thereof.
 2. The compound of formula I, which is 5-ethyl-4-methyl-N-[4-[(2S) morpholin-2-yl]phenyl]-1H-pyrazole-3-carboxamide.
 3. A process for the manufacture of the compound of formula I according to claim 1, which process comprises a) cleaving off the N-protecting group (PG) from compounds of formula

to a compound of formula

wherein PG is a N-protecting group, selected from —C(O)O-tert-butyl (BOC), and, if desired, converting the compounds obtained into pharmaceutically acceptable acid addition salts.
 4. The compound of formula I according to claim 1 for use as therapeutically active substance.
 5. The compound of formula I according to claim 1 for use in the treatment of depression, anxiety disorders, bipolar disorder, attention deficit hyperactivity disorder (ADHD), stress-related disorders, schizophrenia, Parkinson's disease, Alzheimer's disease, epilepsy, migraine, hypertension, substance abuse, addiction, eating disorders, diabetes, diabetic complications, obesity, dyslipidemia, disorders of energy consumption and assimilation, disorders and malfunction of body temperature homeostasis, disorders of sleep and circadian rhythm, and cardiovascular disorders.
 6. The compound of formula I according to claim 1 for use in the treatment of schizophrenia, bipolar disorder or depression.
 7. A pharmaceutical composition comprising the compound of formula I according to claim 1 and pharmaceutically acceptable excipients.
 8. The use of a compound of formula I according to claim 1 for the preparation of a medicament for the treatment of depression, anxiety disorders, bipolar disorder, attention deficit hyperactivity disorder (ADHD), stress-related disorders, schizophrenia, Parkinson's disease, Alzheimer's disease, epilepsy, migraine, hypertension, substance abuse, addiction, eating disorders, diabetes, diabetic complications, obesity, dyslipidemia, disorders of energy consumption and assimilation, disorders and malfunction of body temperature homeostasis, disorders of sleep and circadian rhythm, and cardiovascular disorders.
 9. A method for the treatment of depression, anxiety disorders, bipolar disorder, attention deficit hyperactivity disorder (ADHD), stress-related disorders, schizophrenia, Parkinson's disease, Alzheimer's disease, epilepsy, migraine, hypertension, substance abuse, addiction, eating disorders, diabetes, diabetic complications, obesity, dyslipidemia, disorders of energy consumption and assimilation, disorders and malfunction of body temperature homeostasis, disorders of sleep and circadian rhythm, and cardiovascular disorders, which method comprises administering an effective amount of a compound of formula I as claimed in claim
 1. 10. (canceled) 